While several clinical intervention studies are currently being conducted to investigate the possible cancer chemopreventive effect of beta-carotene, it is possible that other carotenoids could have clinically important cancer chemopreventive effects of equal or greater magnitude. We propose to develop and validate a high-pressure liquid chromatographic (HPLC) assay for six distinct carotenoids in human serum samples. This assay would ultimately be used in cancer epidemiologic research to investigate possible relationships between serum levels of individual and total carotenoids, and the subsequent risk of developing cancer. The specific aims of the project are to: 1) Develop an HPLC assay which quantitates the six most abundant serum carotenoids (lutein, zeaxanthin, beta- cryptoxanthin, lycopene, alpha-carotene, beta-carotene) with adequate sensitivity, selectivity, precision, and accuracy. 2) Determine the stability of these substances in sera stored at - 75 degrees centigrade for up to two years. 3) Determine the diurnal variation in serum carotenoid levels in 30 subjects. 4) Determine the seasonal variation in serum carotenoid levels in 30 subjects. 5) Establish ranges of serum concentrations of these six carotenoids in study participants, and their relationships to dietary ingestion. 6) Extrapolate the effects of diurnal and seasonal variation in serum carotenoid levels upon the precision of estimates of treatment effect and sample size in future epidemiologic studies. The results obtained during this two-year project should enable subsequent observational follow-up studies to be conducted which would investigate the hypothesis that serum individual carotenoid levels are related to the risk of subsequent development of cancer.